Replace single instance of character in a string, leave multiple characters untouched

Question

How would I replace periods with spaces, but preserve ...?

string test = "This.is.a.test...";

test = test.Replace(".", " ");

http://rextester.com/DLEHI1253

Answer 1

You could use this (?<!\.)\.(?!\.)

var regex = new Regex(@"(?<!\.)\.(?!\.)");
var ressult = regex.Replace("This.is.a.test..."," ");
Console.WriteLine(ressult);

Output

This is a test...

Demo here